Hirschsprung Disease
A 9-month-old boy has progressive abdominal distension and passes ribbon-like stools once every 5 to 7 days, dating from the neonatal period. He first passed meconium on the third day of life. His weight has fallen from the 50th to the 3rd percentile. Digital rectal examination reveals a tight empty rectum followed by an explosive gush of liquid stool. Which is the most definitive test to confirm the diagnosis?
- A.Rectal suction biopsyCorrect
- B.Contrast barium enema
- C.Anorectal manometry
- D.Supine abdominal radiograph
Explanation
The combination of delayed passage of meconium beyond 48 hours, chronic constipation with ribbon-like stools, failure to thrive, an empty rectal vault, and an explosive gush of stool after rectal examination is classic for Hirschsprung disease. The underlying defect is failure of craniocaudal migration of neural crest derived cells, leaving an aganglionic distal segment that cannot relax, so the proximal bowel dilates while the affected segment remains contracted. Rectal suction biopsy is the diagnostic gold standard because it demonstrates the histological hallmark of absent submucosal ganglion cells with hypertrophied nerve trunks and increased acetylcholinesterase staining. Contrast enema and plain radiographs are useful screening or initial studies that may show a transition zone or dilated proximal bowel, but neither is confirmatory and both can be normal in very short segment or total colonic disease. Anorectal manometry demonstrating absence of the rectoanal inhibitory reflex is a supportive functional test, yet it is unreliable in young infants and still requires biopsy for confirmation. Hirschsprung disease is strongly associated with trisomy 21 and carries a risk of enterocolitis, which presents with fever, explosive foul stools, and sepsis and is a surgical emergency. Definitive treatment is resection of the aganglionic segment with a pull-through procedure. The key board distinction is initial test versus best test: imaging screens, biopsy confirms.
Why each option
- A.
- Correct. Absence of ganglion cells in the submucosal plexus on rectal suction biopsy is the diagnostic gold standard.
- B.
- A contrast enema may show the transition zone and is a reasonable initial study, but a normal study does not exclude the disease.
- C.
- Absence of the rectoanal inhibitory reflex supports the diagnosis but is technically unreliable in infants and is not confirmatory.
- D.
- A plain film shows dilated bowel loops with absent rectal gas and only raises suspicion; it never establishes the diagnosis.
Reference: Nelson Textbook of Pediatrics, 22nd ed., 2024
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